Foam or mist drilling process



United States Patent 3,1113% FOAM 0R MHST DRHLLING PROCESS Delbert V. Crowley, New York, N.Y., assignor to (Gulf Gil Corporation, Pittsburgh, Pa, a corporation of Pennsylvania No Drawing. Filed Aug. 26, 1959, Ser. No. d36,ii6l 7 Claims. (til. I'M-5%) This invention relates to a method of drilling wells and more particularly to a rotary drilling method using a mist or foam as a circulating medium for removal of cut- .tings from. the borehole.

During recent years, many wells have been drilled using air or other :gas as a circulating medium to remove cuttings from the borehole. The substitution of the gaseous circulating medium for the conventional water or drilling muds results in greatly increased drilling rates and bit life. The principal problem encountered in drilling with a gaseous circulating medium is the flow of water into the borehole. Small amounts of water cause balling of cuttings around the bit which increases the torque required to rotate the bit and also increases the danger of stuck drill pipe. At higher rates of flow, the water rises in the borehole to a level such that the water and cuttings cannot be circulated out of the hole with gas alone.

If the rate of flow of water into the borehole is low, for example, less than 1 to 2 barrels per hour, the balling of the cuttings caused by the water inflow can be overcome by the injection of anti-balling agents into the circulating gas stream. The anti-balling agents are in general materials adapted to alter the surface of the cuttings to prevent their sticking together.

At intermediate inflows of water into the borehole, the anti-balling agents are not effective and it is necessary to convert from straight gas drilling to mist or foam drilling to remove the water and cuttings from the bore 'hole. This is accomplished by the injection of small amounts of foaming agents into the gas stream circulated dovsm the well to the bit. If the rate of water inflow is only slightly higher than the rate at which antiballitng agents are adequate to take care of the water, a small amount of additional water is injected into the system to convert the cuttings around the bit from a pasty mass to a fluid suspension capable of entering a foam or mist. The foaming agents cause the formation in the annulus around the drill pipe of a low density foam or mist which can readily be blown from the borehole by the circulating gas to remove both the inflowing water and cuttings.

At higher water inflow rates, for example, above about 20.0 barrels of Water per hour, foam drilling becomes impractical and it is then the usual practice to convert to drilling with a drilling mud. The bit life, which is usual ly determined by failure of the boa-rings of the bit, and the rates of drilling that can be obtained in foam drilling are less than in gas drilling. Failure of the bearings of the drill bit is indicated by an increase in the torque required to rotate the drill pipe. Moreover, the high velocity stream of moisture-laden air which in deep wells may be at high temperatures, causes severe corrosion of the drill bit which contributes to the short life of the bit in foam drilling as compared with drilling with dry gas as a circulating medium. However, foam drilling allows more rapid drilling than can be obtained with liquid circulating mediums and is advantageous until water flows become excessive.

This invention resides in a rotary drilling process using a mist or foam as a circulating medium in which a foaming agent and a sulfurized organic compound are injected into the stream of the gaseous circulating medium to form with water flowing into the hole a foam or mist, thereby Patented Nov. 26, 1963 2 allowing circulation of cuttings from the hole and increasing the life of the drill bit. For convenience, the term foam drilling is used in the claims to include within its scope drilling procedures in which liquids are removed from the borehole of the well either as a foam or as a mist.

A wide variety of foaming agents have been added to the gaseous circulating medium to convert from straight gas drilling to mist or foam drilling, and can be used in the process of this invention. The particular foaming agent used will depend on the conditions, such as the presence and composition of brines, that may be encountered during drilling. Nonionic, the preferred foaming agents, and anionic surface active agents are sold commercially for mist or foam drilling. Adsorption of cationic foaming agents on the cuttings generally precludes use of cationic foaming agents. If anionic surface active agents are employed as a primary foaming agent, small amounts of nonionic surface active agents may be added to them to counteract the effects of salt and cuttings on the foaming agent. it is preferred to inject the foaming agent into the circulating gas stream in an aqueous solution. The water in which the foaming agent is dissolved can be the water injected into the system to convert from gas to foam or mist drilling. The foaming agent can also be injected directly into the system as a solid or liquid without first dissolving it in Water.

The foaming agents currently used in foam drilling and available ccrrnnercially can be used in the process of this invention. Some of the sulfum'zed compounds added to provide extreme pressure lubrication of the drill bit tend to impair the foaming properties of some of the foaming agents to some extent but do not seriously restrict either the learning agents or the sulfurized compounds that can be used. The nonionic surface active agents useful in this invention are generally prepared by the condensation of fatty alcohols, alkyl substituted phenols, fatty acids, rosin acids, or tall oil with ethylene oxide to form high molecular Weight ethers or esters. The polyoxyethylene chain formed in the condensation reaction imparts water solubility to the foaming agent. Typical nonionic foaming agents that have been used are Triton Xl02, a diisobutylphenoxyethanol manufactured by Rohm and Haas Company; DME, a polyoxyethylene ether of nonylphenol containing 30 ethylene oxide groups per nonylphenol group manufactured by General Aniline & Film Corporation; Sterox AP-80, a polyoxyethylene alkyl ether manufactured by Monsanto Chemical Company; and Synfoam No. 1 and Synfoam No. 2 manufactured by Swift & Company. An example of an anionic foaming agent is Brncol 4150, a sodium sulfo succinate ester of fatty acid alk anolarn-ides manufactured by the Witco Chemical Company. The preparation of such compounds is described in U.S. Patent No. 2,236,529. Alkyl aryl sulfonates are also used commercially as foaming agents in mist or foam drilling in combination with nonionic foam stabilizers. Commercially available foaming agents may be complex compositions which may, for example, contain an anionic foaming agent, a nonionic foaming agent which acts as a foam stabilizer, a buffer for control of the pH, and a corrosion inhibitor.

The amount of foaming agent used during foam drilling depends largely on the rate of Water inflow into the borehole. Whether or not effective foaming is being maintained is indicated directly by the gas pressure required to maintain circulation of the gas. An increase in the pressure at the discharge line from the compressor indicates poor foaming and the building up of a column of water in the annulus of the borehole. A general rule used in the control of the addition of the foaming agent is that the foaming agent should be added in quantities sufficient to reduce the surface tension of the water to approximately of its normal value. The foaming agent is usually injected into the circulating gaseous stream in aqueous solutions containing from about 0.025 to 2% by weight of the foaming agent. The concentration or the foaming agent in the aqueous phase in the annulus of the borehole will, of course, be much lower because of the inflow of water from the formations penetrated into the borehole. Laboratory tests on the concentrations of foaming agents required to give the desired reduction in surface tension indicates that concentrations of the order of 01% are effective.

The sulfurized compounds which can be injected into the circulating medium used in mist or foam drilling to increase the life of the drill bit and reduce corrosion are generally sulfurized unsaturated fatty acids having more than 8 carbon atoms per molecule, sulfurized rosin acids, sulfurized unsaturated fatty alcohols of high molecular weight, sulfurized esters of the unsaturated fatty acids, sulfurized unsaturated fatty acid pitches and sulfurized alkali metal soaps of the unsaturated fatty acids having more than 8 carbon atoms per molecule. Examples of suitable sulfurized unsaturated fatty acids are sulfurized oleic acid, sulfurized linoleic acid, sulfurized linolenic acid, and sulfurized ricinoleic acid. Either single sulfurized compounds or mixtures of sulfurized fatty acids can be used. An example of a preferred sulfurized mixture of fatty acids is sulfurizcd tall oil. Gther sulfurized mixtures of fatty acids suitable for use in this invention can be obtained by the sulfurization of the mixture of acids produced on the hydrolysis of naturally occurring fats and oils such as cottonseed oil, linseed oil, tallow, etc. A preferred group of esters which can be sulfurized for use in this invention are the naturally occurring triglycerides of fatty acids present in animal and vegetable oils. Sulfurized unsaturated esters of monoand di-hydric alcohols also are effective.

The concentration of sulfur in the sulfurized compound may range from about /2% up to the maximum concentration of sulfur that can be introduced into the compound, which, in highly unsaturated compounds, may be as high as 40%, by weight. Compounds containing 2 to 5%, by weight, sulfur are preferred.

The sulfurized compound is preferably injected into the gaseous circulating medium dispersed in the aqueous solution of the foaming agent. It is a unique characteristic of foam drilling that high load carrying capacities, as measured on the Timken wear and lubricant tester, can be obtained with very low concentrations of the sulfurized compounds in the liquid phase injected into the gas stream. Concentrations of sulfurized compounds as low as 0.025% of the liquid injected into the circulating gas stream have been found to be effective in lubricating the drill bit. The maximum concentration of the sulfurized compound used is generally determined by economic factors. it is naturally desirable to use as little as possible of the sulfurized compounds while still obtaining the desired effect of protecting the drill bit. In some instances, high concentrations of a particular sulfurized compound will seriously reduce the foaming properties of a particular foaming agent. It is preferred to use concentrations of sulfurized compounds in the range of .05 to 1% in the aqueous dispersion injected into the circulating gas.

EXAMPLE 1 In a well in Eddy County, New Mexico, after setting inch conductor pipe, 2. hole was drilled to a depth of 154 feet using air as a circulating medium. Because of the encroachment of water into the hole, the hole was mudded and drilled to a depth of 1043 feet using mud as a circulating medium. At that depth, 16 inch surface pipe was cemented and air drilling operations commenced. A 13% inch hole was drilled to a depth of 3550 feet at which depth a gas flow with a small amount of water and oil was encountered. An aqueous solution containing /2 gallon of Tech Chem No. 2, a commercial foaming agent manufactured by General Aniline & Film Corporation, per barrel of water, was injected into the circulating air stream and mist drilling employed to a depth of 3922 feet. At that depth circulation was not maintained with mist drilling and the hole was mudded with a salt water mud. Drilling was continued to a depth of 4487 feet with the salt water mud, at which depth 10% inch casing was set.

Gas drilling was commenced again at 4455 feet using water, driilir" was converted at 5509 feet to mist g by the l jection at the rate of 8 barrels per hour of an aqueous solution containing 3% by weight of Tech No. 2, and one ounce per barrel of Aquaness 211, a corrosion inhibitor manufactured by Atlas lowder Comp ty. As the fluid infiows into the hole increased, the concentration of the foaming agent was increased to .6% by weight with the rate of injection of the water into the circulating gas stream remaining constant. Drilling during the drilling at the interval from 5509 feet to 6800 feet, two other foaming agents, Afrox, manufactured by Hercules Powder Company, and Arfomist, manufactured by Armour 8: Company, were used for short periods.

During the drilling of the interval from 6800 feet to 9427 feet, a sulfurized tall oil containing 2.6% sulfur was dispersed in the solution of the Tech Chem No. 2 foaming agent. The sulfurized tall oil was initially added to the solution of the foaming agent in amounts to give a concentration of the sulfurized tall oil of 1.5% by wu nt. The drilling air pressure increased from 250 psi. to 750 p.s.i. within a few minutes, thereby indicating that effective foaming was not being obtained. The concentration of the sulfurized compound was reduced to .15% which allowed the circulation to be maintained with a drilling air pressure of 275 p.s.i. The average bit life was increased by the addition of the sulfurized compound from 37 hours to 41 hours. The bits were pulled during the drilling of the well immediately upon observation of an increase in the torque required for rotation. In addition to the increased bit life, the sulfurized compound reduces corrosion of the drill pipe and drill collars.

EXAMPLE 2 in a well in the Accident Field in Maryland, mist drilling was commenced at 350 feet. Sterox AP-BO, an active clear liquid nonionic foaming agent of the polyoxyethylene alkyl ether type was added in an aqueous solution to the circulating air to cause the desired mist or foam formation. The concentration of the Sterox AP-80 in the water injected into the circulating air was approximately l% over the period of the test and the water was injected into the circulating air at a rate ranging from 5 to 9 barrels per hour. The foam drilling was continued to a depth of 680 feet. At that depth, the foaming agent was changed to DME and a sulfurized tall oil containing about 2% sulfur was incorporated in the water forming the aqueous solution of DME in a concentration ranging from 0.2 to 1%, and averaging about .75%, during the period of the test. At a depth of 837 feet, at which depth the bit was changed, the foaming agent was changed to a combination of Sterox AP-SO in a concentration by weight of approximately 1% and DME in a concentration by weight of 0.25 to 0.5%. The concentration of the sulfurized tall oil was maintained at approximately .75%. Drilling was continued to a depth of 950 feet at which time the drill bit was pulled for reasons other than its failure. An inspection of the bit showed that approximately /2 of its life had been consumed. A comparison of the average performance of the drill bits used during the foam or mist drilling without the addition of the sulfurized compound with that of the bits used during the foam or mist dr-illing with the addition of the sulfurized compound is presented in Table I. The average for the bits used during the addition of sulfurized compound includes the bit that was pulled before it was The incorporation of the sulfurized compounds described in this specification in the circulating gas stream forms a protective film on the metallic surfaces which provides extreme pressure lubrication of the bearings of worn out, which reduces the reported average perform- 5 the drill bit and protects the drill pipe and drill collars ance of the bits used during the addition of the sulfuriz/ed against excessive COII'OSIOII. The sulfurized compounds Compound below the performance that could be obtained. result in an increase in the number of hours the drill bit T bl I can be used before it must be replaced and also in the a e amount of hole that can be made with a single drill I-I SB't F0 tBit our I 1 e l The conditions existing 1n the annulus surrounding the Foaming Agent Without summed Com drill pipe dur ng the drilling process of this mventron are "T 95 1 not known with certamty. There may be a continuous Fammg Agent Plus summed 4 gaseous phase with a mist dispersed in it, a foam or froth of bubbles in a continuous liquid phase, or a combination Exammatlohs made approx'lmately two Weeks after a of a mist and foam. The terms mist drilling and foam test of blts used during the foam drilhhg P to tha drilling have been used interchangeably to cover drilling introduction of the sullfurized compound with those used operations in hi h a foaming agent ith or without While adding the shlfhl'ized compound Showed that the water is injected into a circulating gas stream to aid in bits used before the introduction of the sulfurized comthe removal of tti d ter from the hole. pound were heavily rusted whereas those used while the 1 l i shlfhl'l'zed Compound Was added to the Circulating 1. In a foam drilling process in which air is circulated maihed y- The shlflh'ized Compound apparently down a borehole in contact with the drill bit and said air forms an adherent coating on the metal surfaces procontains a foaming agent adapted to mix with water tecthlg them from COITOSIOII- in the borehole to form a foam for removal of cuttings A measure of the efielctiveness of Th5 Combination of from the borehole, the improvement comprising injecting the foaming agent and the sulfhlized compound in P the foaming agent in an aqueous solution into the circu- Vidihg lubrication hearings 0f the drill bit can lating air, and dispersing a sulfurized compound selected he Obtained y use of the Timken Wear and lubricant from the group consisting of sulfur'med unsaturated fatty tester- All aqufiOuS 501115011 0f the foaming agent and acids having more than 8 carbon atoms per molecule, sula sulfhriled compound Water in concentrations Cofffifurized rosin acids, sulfurized unsaturated fatty alcohols spondihg t0 the Concentrations in Solutions injected into of high molecular weight, sulfurized esters of unsaturated the circulating air stream in mist OI foam drilling is fatty acids having more than 8 carbon 310mg per molesprayed On ths Wear block of the Timken machine y cule and sulfurized unsaturated fatty acid pitches in the means of a p y The technique for using i116 aqueous solution in an amount of about 0.025 to 1% by Timken machine with liquid lubricants is then followed weight f the solution to form a protective coating on in testing the material sprayed on the wear block. The th surfaces of the drill bit, said sulfurized compound test procedure gives a reproducibility of about 10 pounds containing /2 to 20% sulfur. in the range of 2.0 to 30 pounds on the Timken ma- 2. A method of drilling a well in which 2 to 200 barchine and of about 15 pounds in the range of 80 to rels per hour of aqueous liquids flow from formations 100 pounds. penetrated by the well into the borehole comprising rotat- A series of tests of combinations of different suling a bit at the bottom of the well by means of drill furized compounds with foaming agents were made on pipe extending to the well head, circulating air down the the Timken machine using the machine described above. drill pipe and into contact with the drill bit and upward The results of the tests are set forth in Table H. through the annulus between the drill pipe and the bore- T able II Sulfurized Compound, Percent by Foaming Agent, Percent by Timken Load Run No. Weight Weight Carrying Capacity 0.125 DME 1 F20. 1.0 Sterox AP- F30.9 1.0 Afrox 3 F30. 1.0 Armomist 4 F20. 1.0 Synfoam No. 1 F30. 1.0 Gafen FA-l 5 F209 1.0 Sulf. Oleic Acid, 20% Sulfur 0.25 DME B100. .025 Sulf. Tall Oil, 2% Sulfur 0125 DME P60. .25 Sulf. Tall 011, 2% Su1fur DME P100. 1.0 Sult. Tall 011, 2% Su1fur 1 0 DME P100. 0.5 Sulf. Tall 011, 2% Sulfur- 1 0 Sterox AI 80- P60. 0.5 Sulf. Tall Oil, 2% Sulfur 1 0 Synfoam No 1 P80. 1.0 Sulf. Tall Oil, 2% Sulfur 1.0 Afrox P80. 0.5 Suli. Tall Oil, 2% Sulfur 1.0 Sterox AP-80, 0.5 DME- P60. 0.5 Sulf. Tall Oil, 2% Sulfur.-. 1.0 Gafen FA-l, 0.25 DME. P40. 0.75 Sulf. Tall Oil, 2% Sulfur- 1.0 Sterox AP-SO, 0.5 DME- P100. 1.0 Sulf. Tall 011, 2% Sulfur 1.0 Sterox AP-BO P100. 1.0 Glycerol 'Irioleate, 10% Sulfur- 0.3 Gafen FA1 P80. 1.0 Glycerol Trioleate, 10% Sulfur. 0.3 DME P60. 1.0 Sulf. lard oil, 17% Sulfur 0.3 DME P60. 1.0 Sulf. lard oil, 17% Sulfur 0.3 Galen FA-l P100.

F=fall; P =pass DME, General Aniline & Film Corporation, a nonionlc ethylene oxide derivative of nonylphcnol. Sterox AP-80," Monsanto Chemical Company, a polyoxyethylene alkyl ether. Afrox," nonionic foaming agent manufactured by Atlas Powder Company, ethylene oxide derivative of trldecyl alcohol.

4 Armomist," commercial foaming agent manufactured by Armour & Company.

5 Synfoam No. 1, nonionic foaming agent manufactured by Swift & Company.

B Gafen FA-l, commercial foaming agent manufactured by General Aniline & Film Corporation.

7 The aqueous phase was a brine containing 5% sodium chloride and 1% calcium sulfate.

8 The aqueous phase was a brine containing 5% sodium chloride and .6% calcium sulfate.

9 In these runs the reading given is the lowest made during the test of the load carrying capacity of the foaming agent. None of the foaming agents passed any of the tests to which they were subjected.

hole wall of the well, and injecting into the air delivered down through the drill pipe an aqueous medium containing about (3.025 to 2% by weight of a foaming agent and about 0.05 to 2% of a sulfurized compound containing /2 to 40% sulfur by weight selected from the group consisting of sulfurized unsaturated fatty acids having more than 8 carbon atoms per molecule, sulfurized rosin acids, sulfurized unsaturated fatty alcohols of high molecular weight, sulfurized esters of unsaturated fatty acids having more than 8 carbon atoms per molecule and sulfurized unsaturated fatty acid pitches, the rate of injecting the aqueous medium into the circulating air stream being sufiicient to produce a concentration of at least 0.01% of foaming agent in the aqueous fluids in the annulus of the well whereby a foam is formed in the annulus of the well for lifting cuttings through said annulus.

3. A process as set forth in claim 2 in which the foaming agent is a nonionic foaming agent.

4. A process as set forth in claim 2 in which the foaming agent is an anionic foaming agent.

5. A process as set forth in claim 2 in which the foam- 8 ing agent is a sodium sulfo succinate ester of fatty acid alkanolamides.

6. A foam drilling process as set forth in claim 1 in which the sulfurized compound is a sulfurized unsaturated fatty acid having more than 8 carbon atoms per molecule.

7. A process as set forth in claim 1 in which the sulfurized compound is sulfurized tall oil.

References Cited in the file of this patent UNITED STATES PATENTS 2,701,122 Grable Feb. 1, 1955 2,773,030 Tailleur Dec. 4, 1956 3,014,862 Taillcur Dec. 26, 1961 3,027,324 Rosenberg Mar. 27, 1962 OTHER REFERENCES Randall et al.: Stearates, Foaming Agents Combat Water in Air or Gas Drilling, Oil and Gas Journal, Nov. 3, 1958. 

1. IN A FOAM DRILLING PROCESS INWHICH AIR IS CIRCULATED DOWN A BOREHOLE IN CONTACT WITH THE DRILL BIT AND SAID AIR CONTAINS A FOAMING AGENT ADAPTED TO MIX WITH WATER IN THE BOREHOLE TO FORM A FORM FOR REMOVAL OF CUTTINGS FROM THE BOREHOLE, THE IMPROVEMENT COMPRISING INJECTING THE FOAMING AGENT IN AN AQUEOUS SOLUTION INTO THE CIRCULATING AIR, AND DISPERSING A SULFURIZED COMPOUND SELECTED FROM THE GROUP CONSISTING OF SULFURIZED UNSATURATED FATTY ACIDS HAVING MORE THAN 8 CARBON ATOMS PER MOLECULE, SULFURIZED ROSIN ACIDS, SULFURIZED UNSATURATED FATTY ALCOHOLS OF HIGH MOLECULAR WEIGHT, SULFURIZED ESTERS OF UNSATURATED FATTY ACIDS HAVING MORE THAN 8 CARBON ATOMS PER MOLECULE AND SULFURIZED UNSATURATED FATTY ACID PITCHES IN THE AQUEOUS SOLUTION IN AN AMOUNT OF ABOUT 0.025 TO 1% BY WEIGHT OF THE SOLUTION TO FORM A PROTECTIVE COATING ON THE SURFACES OF THE DRILL BIT, SAID SULFURIZED COMPOUND CONTAINING 1/2 TO 20% SULFUR. 